Heap leaching is an industrial mining process used to extract metals from ore. Mined ore may be crushed into small chunks and heaped onto an impermeable plastic and/or clay lined leach pad. The heap of ore is irrigated with leaching solutions or lixiviants capable of dissolving the desired metals residing in the ore. As the lixiviant proceeds downwardly through the heap, an enriched or pregnant solution containing the lixiviant and the desired metals is created. The use of low permeability liner systems beneath the heap maximizes solution recovery and protects underlying groundwater conditions.
The pregnant solution proceeds downwardly (by gravity flow) through the heap where it may be retrieved using lined basins, sumps, and/or ponds for subsequent processing and recovery. After the desired metals are separated from the pregnant solution, the resulting barren solution or dilute lixiviant may be re-circulated to the heap for use in subsequent heap leaching operations. The barren solution may also be subjected to further treatment and/or removal of residual metals. Heap leaching operations may also be conducted under unsaturated liquid flow conditions wherein air flowing upwardly through the heap is utilized in conjunction with the lixiviant.
In-situ leaching is a mining process used to recover desired materials such as copper and uranium through wells drilled into a formation. Leaching solutions or lixiviants are pumped into the formation so that they come in contact with the desired materials. Explosive and/or hydraulic fracturing techniques may be used to create open pathways for the lixiviants in the formation. Pregnant solution bearing the lixiviant and the dissolved desired materials may then be pumped to the surface and processed. This process allows the extraction of desired materials from the formation without the need for conventional mining involving drill-and-blast, open-cut or underground mining.
One of the challenges faced when harvesting metals during leaching operations is accurately determining the location of the pregnant solution and the concentration of desired metals or materials with in the heap/formation. For example, it may be difficult to predict the location of the pregnant leach solution, how high the plume is and when it will start to decline in metal concentration. Further, it may be difficult to monitor how efficiently desired metals or materials are leached from the heap/formation. There remains a need for a system and method capable of accurately monitoring the effectiveness and efficiency of leaching processes in a real time environment.